Assessment of Pesticide Residues in Fresh Vegetables from Three Major Markets in Lagos Using QuEChERS Method and GC-MS

Abstract

The study evaluates pesticide residues in fresh vegetables from three major markets in Lagos and verified compliance of these fresh vegetables with the maximum residue levels (MRLs) as specified by Codex Alimentarius Commission. The residues were extracted by means of multi residue method based on the Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method, Gas Chromatography - Mass Spectrometry (GC-MS) was used to determine two organophosphates (dichlorvos and chlorpyrifos), two organochlorines (endosulfanII and chlorothalonil), two carbamates (carbaryl and carbofuran) and two pyrethroids(alpha-cypermethrin and lambda-cyhalothrin). Fifteen samples of five common vegetables (cabbage, lettuce, fluted pumpkin, bitter leaf and African spinach) were analyzed. The linear ranged used were 0.005, 0.1, 0.25, 0.5 and 1.0mg/l, resulting to r2 of ≥0.996. While the mean recoveries obtained for two fortification levels (0.1 and 0.25 ppm) in three replicates for lettuce control sample and spinach control sample were 96.7 to 104.3%, 96.3 to 101.3%, and 92.0 to 114.3% ,92.1 to102.1% respectively. A satisfactory precision of RSD<20% was recorded. The limit of detection (LOD) and limit of Quantitation (LOQ) were between 0.005 -0.050 mg/kg and 0.015-0.150 mg/kg respectively. Pesticide residues detected ranges from 0.025-0.529 mg/kg. EndosulfanII, Chlorothalonil, carbaryl and Carbofuran were not detected during the entire study. However, pesticide residues detected were below the MRLs specified by Codex Alimentarius Commission.